Leak indicator with test leak and test leak for integration into a leak indicator

ABSTRACT

A leak indicator including a housing that houses components of the indicator as well as a test leak, and test leaks that are suitable for integration into a leak indicator.

FIELD OF THE INVENTION

The present invention relates to a leak indicator having thecharacteristics of patent claim 1 as well as a test leak having thecharacteristics of patent claim 11 suitable for integration into a leakindicator.

BACKGROUND OF THE INVENTION

Stringent requirements as to leaktightness are imposed on many systemsand products in industry and research. It depends on the type of leak,leak rate or the size of the leak which leak searching method isapplied, respectively, which leak indicator is employed.

In the instance of units under test or subassemblies manufactured in therefrigerants, automotive or other industries, the method of sniffer leakdetection is frequently employed. This requires, that there be presentin the unit under test or subassembly a test gas, preferably at anoverpressure. Frequently helium is employed as the test gas, which isintroduced before sealing into the hollow spaces which are to beanalysed for the presence of leaks. It is also known to employ gasespresent anyway in the units under test or subassemblies as the test gas,for example SF6 or halogen gases in the refrigerants industry.

The unit under test which is to be analysed for the presence of leaks isscanned with the aid of the intake point (tip) of a sniffer gun, wherebysaid tip accepts the test gas escaping from a possibly present leak andsupplies it to a test gas detector. This test gas detector may beaccommodated together with other components within an instrument towhich the sniffer gun is linked, among other things, through a hose. Ifthe detector is sufficiently small (for example, an infrared gasanalyser) then it also may be accommodated in the gun itself, therebysignificantly reducing the response time.

Test gas leak indicators need to be calibrated frequently. To this endit is known to employ test leaks exhibiting a defined leakage. Testleaks for these purposes comprise a gas reservoir and a constriction ofknown conductance. To calibrate a leak indicator with a sniffer gun, thesniffer tip is brought in to the vicinity of the constriction, and theleak rate indication is adjusted.

Test leaks should exhibit, over a time which is as long as possible(significantly over one year), a constant gas flow and should be,moreover, so small that they can be accommodated within the housing of aleak indicator. This requires that the test gas be present in the testleak at a high pressure (8 bar and more). Test leaks of this kind aretemperature sensitive. This applies in particular when the test gas isin the liquid state at the pressures stated. For safety reasons, amaximum temperature must not be exceeded. Installing a test leak of thiskind within a leak indicator in which heat generating components arepresent, causes problems.

SUMMARY OF THE INVENTION

It is the task of the present invention to install the test leak in sucha manner within the housing of a leak indicator that the risk ofexceeding maximum permissible temperatures does not exist, and/or todesign the test leak itself such that even in the instance of exceedingpermissible temperatures a hazard to the users of the leak indicatorwill not exist.

According to the present invention, the partial task of safelyinstalling the test leak within the housing of a leak indicator issolved. Through these means it is achieved that the test leak can notattain higher temperatures compared to the ambient temperature. Themaximum temperature of the test leak is then at the same time themaximum permissible operating temperature for the leak indicator itself.

The further partial task affecting the design of the test leak is alsosolved according to the invention. Through the outer housing it isensured that even when exceeding the maximum permissible temperaturesfor the pressurised vessel, a hazard to persons present in the vicinityof the test leak is excluded.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages and details of the present invention shall beexplained with reference to the examples of embodiments depictedschematically in drawing FIGS. 1 and 2.

FIG. 1 illustrates a sniffer leak indicator according to the presentinvention with components contained therein and

FIG. 2 is a sectional view through a test leak in accordance with thepresent invention.

DETAILED DESCRIPTION

The leak indicator 1 depicted in drawing FIG. 1 comprises a housing 2 inwhich the instrument components are accommodated. Presented by way ofblocks are, for example, a vacuum pump 3, a power supply 4, the gasdetector 5 and a control unit 6. Located outside of the housing is thesniffer gun 7 with its intake point (tip) 8. It is linked via a hose 9to the gas detector 5. In the instance of the gas detector 5 beingaccommodated within the sniffer gun 7, it is linked to the control unitvia signal lines.

All instrument components are accommodated in the upper section of thehousing 2. The housing 2 itself is equipped in the area of the bottom 11and in the upper area with cooling air inlets 12 respectively air slots13. Since at least some of the instrument components generate heat, acooling air flow (arrows 14) is produced through the rising air alone.Should this flow not suffice, an additional fan 15 may be providedsupporting the flow of cooling air. In the depicted example of anembodiment, said fan is located beneath the instrument components. With16 a filter mat is designated through which the taken in cooling air iscleaned. Located above the filter mat 16 is a separating plane 17equipped with air penetration openings, said separating plane limitingtowards the bottom the partial space 18 within the housing with theinstrument components 3 to 6.

With 20 the test leak is designated which is accommodated within theleak indicator 1. Said test leak is located below the separating plane17, so that it is located within an insulated partial section 19 of thehousing being thermally separated from partial section 18 of thehousing. Fresh cooling air continuously flows around said test leak. Theseparating plane 17, directly above the test leak 20 does not exhibitany penetration openings, as well as the filter mat 16 support thethermal insulation of the partial section 19 of the housing from thepartial section 18. The test leak 20 may attain at most the temperatureof the ambient air.

The test leak 20 has a pipe connection 21 which penetrates the housing 2towards the outside. The pipe connection 21 forms a commonlycontinuously open connection between the constriction of the leakindicator 20, said constriction not being depicted in drawing FIG. 1,and an opening 22 suited for introducing the sniffer tip 7. Thisarrangement allows to calibrate the leak rate readout at any time.

It is especially expedient to equip a test leak 20 suited forinstallation within a leak indicator 1 with a gas reservoir 31 and aconstriction 33,—for example, in the vicinity of its constriction—with atemperature sensor 23, said temperature sensor being linked (lines 24)to the control unit 6. These measures allow to take into account thetemperature dependent penetrability of the constriction of the test leak20 when calibrating the leak rate readout. In particular, in theinstance of test leaks with a diaphragm as the constriction, taking intoaccount the above is of significance, since the penetrability of thediaphragm is exponentially temperature dependent.

Now in order to attain a reliable calibration of the leak indicator, thetemperature dependence of the test leak is compensated through acorrection curve embedded in the software of the instrument (controlunit 6). The temperature is measured in the area of the test leak. Forthis purpose there is located at the bottom of the test leak a printedcircuit board with the temperature sensor and an EEPROM. In drawing FIG.1 the EEPROM is depicted schematically and designated as 25.

The advantage of the concept detailed, is thus that a compact test leakfor integration into small benchtop units can be produced in acost-effective manner. Since in the EEPROM production date, fillingquantity as well as leak rate are saved, it is possible to estimate thepoint of time at which the reservoir has emptied itself and thus thetest leak must be exchanged.

Drawing FIG. 2 depicts an especially well-suited test leak 20 forinstallation into a leak indicator in accordance with drawing FIG. 1.Said test leak comprises an inner pressure vessel 31 with the gasreservoir. This is a commercially available pressure cell which containsthe desired test gas in the liquid state. The pressure in filledcartridges of this kind is severely temperature dependent. Commonly itmust not exceed 8 bar (test pressure 12 bar). The maximum temperature towhich pressure cells of this kind may commonly be exposed is limited to50° C.

In spite of this, in order to be able to employ pressure vessels of thiskind also at times at higher ambient temperatures as a gas reservoir fortest leaks, a second outer housing 32 is provided. It consists, forexample, of steel and is rated for significantly higher pressures than 8(respectively 12) bar. In the area of one face side it exhibits theconstriction 33 being designed by way of a diaphragm 34. There thenfollows the pipe connection 21 already detailed in connection withdrawing FIG. 1. In the area of the other face side there is provided areleasable cap 35 which preferably may be unscrewed. It allows to closethe releasable housing 32 in a sealed manner. Located between its faceside opening and the cap 35 is a sealing ring 36. After detaching thecap 35, the inside of the housing 32 is accessible for inserting orremoving the pressure vessel 31.

In the area of the face side opposing the cap 35, the housing 32 isequipped with a flange 37 projecting towards the inside. This flangecarries on its side facing the pipe connection 21, the diaphragm 34. Onthe side of the flange 37 facing the cap 35, the pressure vessel 31,inserted into the housing 32, is supported.

In the example of the embodiment depicted in drawing FIG. 2, thepressure vessel 31 is equipped with a ball valve 38 being located in oneof its face sides. The pressure vessel 31 is inserted in such a mannerinto the housing 32 that the valve 38 faces the cap 35. The cap 35 isequipped with a pin 39 assigned to the valve 38, the length of said pinbeing so selected that it opens the valve 38 when the cap 35 iscompletely screwed on. When employing a pressure vessel without valve38, there is provided at the location of the pin 39 a spike whichprovides the pressure vessel 31 with an opening upon closing the cap 35.After closing the cap, either the valve 38 is open or the openingprovided by the spike is present, so that the test gas may flow into thehousing 32. Crucial to the magnitude of the temperature load is now nolonger the pressure vessel 31, but the housing 32 instead.

If it is required to replace the pressure vessel 31, the housing 32 isopened by unscrewing the cap 35. The rim of the cap is provided in thevicinity of its upper side with a small bore 40. This allows, beforefinally unscrewing the cap 35, the pressure to be equalised between theinside of the housing 32 and the surroundings.

The special advantage of the test leak in accordance with the presentinvention is such that the pressure resistant housing 32 will not haveto be replaced. With respect to its stability it may be rated accordingto the desired requirements. Only during transportation and maintainingthe pressure vessel 31 in stock, need the relatively low ambienttemperatures be taken into account. Also the constriction (diaphragm 34)does not belong to a non-reusable product. This offers the advantagethat when changing the gas reservoir, the leak rate of the test leakdoes not change.

In addition, the test leak is optimally protected when being installedaccording to the present invention within a leak indicator. Also theguidance of the cooling air for the instrument over the test leakensures as the maximum temperature, the ambient temperature in the areaof the test leak.

1. Leak indicator comprising a housing which houses components of theindicator and a test leak, wherein the test leak is located below theinstrument components and in which cooling air flows through the housingfrom the bottom to the top wherein for the purpose of supporting thecooling air flow, a fan is provided wherein a separating wall in thehousing is provided, said wall being equipped with penetration openings,which separates an upper partial section of the housing from a lowerpartial section of the housing including a filter mat located in thearea of the separating wall.
 2. Equipment according to claim 1, whereinthere are located within the upper partial section of the housinginstrument components, and where the test leak is located in the bottompartial section of the housing.
 3. Equipment according to claim 1,including a constriction of the test leak that is a diaphragm. 4.Equipment according to claim 1, including a temperature sensor assignedto the test leak, said sensor being linked to a control unit. 5.Equipment according to claim 1, wherein said equipment is designed as asniffer leak indicator and in which a sniffer gun is linked toinstrument components accommodated in the housing.
 6. Equipmentaccording to claim 5, wherein the test gas detector is accommodatedwithin the sniffer gun.
 7. Leak indicator comprising a housing whichhouses components of the indicator and a test leak, wherein the testleak is located below the instrument components and in which cooling airflows through the housing from the bottom to the top wherein saidequipment is designed as a sniffer leak indicator and in which a sniffergun is linked to instrument components accommodated in the housingwherein the test leak is equipped with a pipe connection projectingthrough the housing to the outside and having an opening suited forintroducing the intake point of the sniffer gun.
 8. Equipment accordingto claim 7, wherein for the purpose of supporting the cooling air flow,a fan is provided.
 9. Equipment according to claim 7, wherein aseparating wall in the housing is provided, said wall being equippedwith penetration openings, which separates an upper partial section ofthe housing from a lower partial section of the housing.
 10. Equipmentaccording to claim 9, wherein there are located within the tipperpartial section of the housing instrument components, and where the testleak is located in the bottom partial section of the housing. 11.Equipment according to claim 9, including a filter mat located in thearea of the separating wall.
 12. Equipment according to claim 7,including a constriction of the test leak that is a diaphragm. 13.Equipment according to claim 7, including a temperature sensor assignedto the test leak, said sensor being linked to a control unit. 14.Equipment according to claim 7, wherein the test gas detector isaccommodated within the sniffer gun.